68Ga-PSMA PET/CT Protocols May Differ for RP, BCR

New research suggests that men with PSA level persistence after undergoing radical prostatectomy (RP) should be recommended 68Ga-PSMA PET scans even if their PSA level is considered low.

Whereas patients with biochemically recurrent (BCR) prostate cancer after RP should be monitored based on their PSA levels, as additional scans may not provide benefits.

A study presented at the 37th congress of the European Association of Urology in Amsterdam analyzed 207 patients with prostate cancer who received 68Ga-PSMA PET/CT. Researchers found that the PSA levels of patients, as well as the time to BCR during PSMA PET/CT, can have an effect on the chances of positive findings during PSMA PET.

Patients were organized by their time to BCR, and researchers examined the correlation between PSA level at the time of PSMA PET and the likelihood of positive results. The median level of PSA at the time of PSMA PET/CT was 1.0 ng/ML. In the study, 38% of patients had early BCR or PSA persistence after RP.

A high PSA level and early versus late BCR at the time of PSMA PET was associated with a 2.2- and 2.6-fold increased odds of positive results. In patients with early BCR, the chance of receiving positive PSMA PET results was high even when their PSA levels were considered low, and their results continued to increase with a higher PSA level; the positive findings rate increased from 63% to 93%. Moreover, in patients with late BCR, the probability of receiving positive findings was lower than 40% if PSA values were under 0.5 ng/ml.

José Ramón García Garzón, MD, of Ascires Cetir Viladomat in Barcelona, said that “it is important to know which patients may benefit the most; screening in relation to the time after PSA elevation and the PSA value is an appealing strategy to increase the sensitivity of the test.”

Professor Otis W. Brawley, MD, of Johns Hopkins University in Baltimore, noted that “some patients are insisting on [PSMA PET scans] for routine evaluation of response…some want them with very low PSA’s where chances of a false negative are high. When doctors do not have guidelines as to when a test should be used and there is a lot of patient request, things are ripe for waste and abuse.”

To counteract unnecessary PSMA PET use, low-risk patients and those with late BCR should be monitored closely based on their PSA levels to determine if they would benefit from additional PSMA PET scans.